This invention relates generally to disc-type valve assemblies, and more particularly, to a combination valve stem and valve disc, and to a method of assembling same in a disc-type valve housing.
In disc-type valve assemblies constructed for straight through or right angle flow therethrough, an elongate threaded valve stem is commonly mounted in a threaded valve guide in the valve housing such that the stem distal end extends into the flow passageway. In normal construction, a valve disc is loosely mounted to that distal end of the valve stem. As the stem is threaded further into the flow passageway, the valve disc is positioned to sealingly engage a valve seat which is formed in the valve passageway in axial alignment with the valve guide. The valve disc is preferably loosely fitted to the valve stem to compensate for irregularities in the alignment of the valve assembly parts. Heretofore, in most valve stem-disc mounting arrangements, the valve disc is formed with a hollow mounting portion into which the distal end of the valve stem is inserted. Prior art improvements in valve stem-disc combinations generally relate to either (1) the insertion of the stem into the disc, or (2) the retention of the disc on the stem.
In one known valve stem-disc combination, the disc is held on the valve stem by means of several retainer pins and a retainer ring which holds the pins within radially extending slots in the valve seat disc and with an annular groove positioned adjacent the distal end of the valve stem for receiving the pins. This valve stem-disc combination is a comparatively complicated assembly which is shown and described in U.S. Pat. No. 2,470,700, issued to the assignee to the present application.
Another means of mounting a valve disc upon a valve stem is shown and disclosed in U.S. Pat. No. 3,700,206, issued to the assignee of the present application, wherein the valve disc is a one-piece molded plastic member having a slot therein in which the distal end of the valve stem, which is shaped like a button, is inserted. The valve disc includes several biased arms in the path of insertion which prevent the removal of the valve stem button from the disc once it is inserted therein. In certain instances, discs made of steel are preferable to those made of plastic materials.
In another valve stem-disc combination, the disc includes a valve stem mounting hole which is chamfered or angularly tapered to open toward the top of the hole as a guide for a valve stem to be inserted therein. An annular indent groove is positioned around the circumference of the stem mounting hole inwardly adjacent the chamfered portion. The cylindrical distal end of the valve stem includes a flat end surface which is positioned generally perpendicular to the axis of the stem, and an annular indent groove on the circumference of the stem inwardly adjacent the distal end thereof in which a retaining ring is loosely mounted. As the stem's distal end and the loose retaining ring are inserted into the stem mounting hole of the disc, the chamfered surface of the mounting hole attempts to center the valve stem and the retaining ring for full insertion therein. However, if the loosely fitting retaining ring is positioned off-center in its annular groove, the retaining ring may strike the top of the disc and bind thereon preventing the insertion of the stem into the disc mounting hole until the retaining ring is manually centered in the stem groove.
It is therefore an object of the invention to provide an improved combination valve stem and valve disc for a disc-type valve assembly.
Another object of the invention is the provision of an improved method of mounting a valve disc to a valve stem in a disc-type valve assembly.
A further object of the invention is the provision of a valve stem which is structured to be inserted into a mounting hole in a valve disc without binding on the disc before insertion is complete.